Ultrasonic detection system

An ultrasonic detection system, comprising means for emitting a train of ultrasonic wave pulses in all peripheral directions, means for receiving said ultrasonic wave pulses reflected back from the respective directions by means of rotating directivity and producing a reception signal and means for indicating said reception signal on a cathode ray tube screen scanner circularly in synchronism with the emitted ultrasonic wave pulses, said system further comprising means for generating a train of low frequency pulses, a reversible counter circuit for counting said low frequency pulses, means for inverting said reversible counter circuit at two different counts of said reversible counter circuit, means for indicating a radial bright line on said screen in response to each count output of said reversible counter circuit, and means for sampling said reception signal in response to each of said count outputs and producing an audible signal in response to said sampled reception signal, whereby a simulated radial bright line is reciprocated between two directions corresponding to said two different counts of said reversible counter circuit and, at the same time, the presence of the reception signal in the direction of said bright line is audibly signalled.